Windows 8 users may not have the option to buy a full retail copy of the operating system when it launches this October.

That's according to Microsoft insiders Mary Jo Foley and Paul Thurrott, who both say they've heard that full retail copies of Windows 8 won't be available. The Verge first spotted their remarks on TwiT TV's Windows Weekly show.

Users who aren't upgrading from an older version of Windows 8 may instead have to purchase an OEM version, which is typically reserved for hardware makers and sellers who bundle the software with their computers. This version may be referred to as a “System Builder” edition of Windows, and would make sense for users who build their own PCs or want to run Windows 8 on Mac hardware.

The good news is that OEM versions of Windows are cheaper than full retail copies, and while Microsoft has never really cracked down on consumers who buy these versions, doing so isn't fully legitimate. With Windows 8, Microsoft may fully sanction the practice.

On the downside, OEM versions of Windows are locked to a single motherboard, so they can't be transferred between machines. That means that if you replace your homemade PC, you need a new copy of Windows. And while retail copies include 90 days of support from Microsoft, with an OEM version, you're on your own. It's unclear if either policy will change with Windows 8.

In any case, Microsoft hasn't announced standalone or OEM pricing for Windows 8. Users who upgrade from a PC running Windows XP or higher can get the new software for $40 through January 31, 2013.